From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- arch/powerpc/perf/callchain.h | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) create mode 100644 arch/powerpc/perf/callchain.h (limited to 'arch/powerpc/perf/callchain.h') diff --git a/arch/powerpc/perf/callchain.h b/arch/powerpc/perf/callchain.h new file mode 100644 index 000000000..19a8d051d --- /dev/null +++ b/arch/powerpc/perf/callchain.h @@ -0,0 +1,35 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +#ifndef _POWERPC_PERF_CALLCHAIN_H +#define _POWERPC_PERF_CALLCHAIN_H + +void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry, + struct pt_regs *regs); +void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry, + struct pt_regs *regs); + +static inline bool invalid_user_sp(unsigned long sp) +{ + unsigned long mask = is_32bit_task() ? 3 : 7; + unsigned long top = STACK_TOP - (is_32bit_task() ? 16 : 32); + + return (!sp || (sp & mask) || (sp > top)); +} + +/* + * On 32-bit we just access the address and let hash_page create a + * HPTE if necessary, so there is no need to fall back to reading + * the page tables. Since this is called at interrupt level, + * do_page_fault() won't treat a DSI as a page fault. + */ +static inline int __read_user_stack(const void __user *ptr, void *ret, + size_t size) +{ + unsigned long addr = (unsigned long)ptr; + + if (addr > TASK_SIZE - size || (addr & (size - 1))) + return -EFAULT; + + return copy_from_user_nofault(ret, ptr, size); +} + +#endif /* _POWERPC_PERF_CALLCHAIN_H */ -- cgit v1.3.1